ATOMIC STRUCTURE An atom is the smallest particle of matter that retains the properties of the element. An atom is composed of ______ subatomic particles.

ATOMIC STRUCTURE In a neutral atom, the # of electrons must equal the # of ___. The identity of the atom is based on the # of _________________. PARTICLEMASSCHARGE ELECTRONVirtually none (1/1840) Negative PROTON1 AMUPositive NEUTRON1 AMU (slightly more massive than proton) neutral

ATOMIC STRUCTURE When atoms of the same element contain different #s of neutrons they are called __________. An atom has an overall charge of ____. When an atom loses or gains electrons, an ___________ forms. A cation forms when an atom loses electrons. (+ charge) An anion forms when an atom gains electrons. (- charge)

Nucleus Contains Protons (p + ) and Neutrons (n) the mass of the atom Electron Cloud Region around nucleus where electrons (e - ) move the volume of an atom Atomic Structure 1 st energy level (2 e - ) 2 nd energy level (8 e - ) 3 rd energy level (18 e - ) 4 th energy level (32 e - )

Electron Energy Levels ENERGY LEVEL# OF ELECTRONS 12 electrons 28 electrons 318 electrons 432 electrons 5 Valence electrons are the electrons in the outer most energy level.

C Atomic Number: # of protons in nucleus (also the # of electrons) Average Atomic Mass: average mass of the mixture of isotopes Chemical Symbol: abbreviation for the name of an element (1 st letter caps, 2 nd letter lower case)

12 6 C 14 6 C Mass Atomic number Isotopes of Carbon

Atomic Calculations Element Atomic # # of Protons # of Electrons Charge on nucleus Mass number Number of neutrons He